<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="https://unpkg.com/element-ui/lib/theme-chalk/index.css">
</head>
<body>
<div id="app">
    <el-upload
            class="upload-demo"
            action="/upload"
            :on-preview="handlePreview"
            accept=".pdf"
            :limit="10">
        <el-button size="small" type="primary">点击上传</el-button>
        <div slot="tip" class="el-upload__tip">只能上传pdf文件</div>
    </el-upload>
</div>

<!--<script src="https://unpkg.com/vue/dist/vue.js"></script>-->
<script src="https://cdn.staticfile.org/vue/2.2.2/vue.min.js"></script>
<script src="https://unpkg.com/element-ui/lib/index.js"></script>
<script>
    new Vue({
        el:"#app",
        methods:{
            handlePreview(file){
                window.open(file.response.url)
            }
        }
    })
</script>
</body>
</html>